Packet Multiple Access SHARED UPLIN TERMINAL APPL TERMINALL TRANS NET LLC DLC MAC

Sampling Given a continuous time waveform, can we represent it using discrete samples? How often should we sample? Can we reproduce the original waveform?

9.1 消声器性能评价 9.2 消声器的分类和消声机理 9.3 消声设计 9.4 消声设计工程实例

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工程实例: 连杆、螺栓、桁架、房屋立柱、桥墩……等等。 力学特征: 构件：直杆 外力：合力沿杆轴作用(偏离轴线、怎样处理?)

Administrative matters Instructors: Eytan Modiano Meeting times: Tuesdays and Thursdays Text: Communications Systems engineering Proakis and salehi Grading 10% weekly Homework Assignments 30% each of 3 exams Final exam during final exam period

Sampling Sampling provides a discrete-time representation of a continuous waveform Sample points are real-valued numbers In order to transmit over a digital system we must first convert into discrete valued numbers

Automatic repeat request (ARQ) Break large files into packets FILE PKT PKT PKT Check received packets for errors Use a feedback channel to request retransmissions Retransmit packets containing errors acket Receive ACK